Cutting device and cutting method

ABSTRACT

Cutting machining is performed on a workpiece by making a cutting tool travel relative to the workpiece while rotating the cutting tool such that a peripheral speed of the cutting tool becomes equal to or more than a cutting speed of the cutting tool, while an outer peripheral surface and an end surface of the cutting tool function as a rake surface and a relief surface, respectively.

The present application is a divisional application of U.S. patentapplication Ser. No. 15/320,222, filed Dec. 19, 2016, which is a U.S.national stage of PCT/JP2015/068182 filed on Jun. 24, 2015, which claimspriority under 35 U.S.C. § 119(b) to Japanese application 2014-132119filed on Jun. 27, 2014 and Japanese application 2015-121362 filed onJun. 16, 2015.

TECHNICAL FIELD

This invention relates to a cutting device and a cutting method.

BACKGROUND ART

In a cutting device, when a cutting machining is performed with acutting tool, such as a cutting tool or the like, on a workpiece made ofa difficult-to-cut material, such as Titanium alloy or Inconel, acutting edge of the cutting tool is kept in contact with the workpiecefor a long time with a large cutting resistance force. Accordingly,cutting heat at a high temperature tends to be generated at thecontacting portion of the cutting edge. This may cause a deteriorationof the tool life.

Under such situation, a rotary cutting method has been proposed, forexample, in a Patent Literature 1, in which a rotation axis of arotatable round-plate shaped cutting tool is arranged in parallel with acutting traveling direction and the cutting machining is performed onthe workpiece, with rotation of the cutting tool, making an end surfaceof the cutting tool functioning as a rake surface. According to thisrotary cutting method, since the cutting tool is rotated, the cuttingheat generated on the cutting edge is dispersed in the entirecircumference, thereby to improve the tool life.

CITATION LIST Patent Literature

Patent Literature 1: JP2006-68831 A.

SUMMARY OF INVENTION Technical Problem(s)

According to the rotary cutting method under the state of art, a highlyefficient cutting machining can be performed. However, wear of thecutting edge is tremendous and further improvement in the tool life isstill required. Further, according to the rotary cutting method, sincethe rotation axis of the cutting tool is arranged in parallel with thecutting traveling direction, an influence of a rotation deflection ofthe cutting tool during cutting machining may be easily transferred onto the surface of the workpiece to be cut. Thus, an issue of worseningof the cutting accuracy of the cutting surface of the workpiece has beenraised on this method.

The present invention has been made considering the above circumferencesand it is an object of the invention to provide a cutting device and acutting method which can achieve further improvements in extending acutting tool life and at the same time which can achieve a high accuracyon cutting machining surface.

Solution to Problem(s)

(Cutting Device)

The cutting device according to the present invention includes arotating means for rotating a cutting tool about a rotation axis of thecutting tool and a traveling means for making the cutting tool travelrelative to a workpiece, wherein the rotating means and the travelingmeans perform a cutting machining on the workpiece by making the cuttingtool travel relative to the workpiece while rotating the cutting toolsuch that a peripheral speed of the cutting tool becomes equal to ormore than a cutting speed of the cutting tool, having an outerperipheral surface and an end surface of the cutting tool function as arake surface and a relief surface, respectively.

According to the cutting machining by the above cutting tool, across-cutting function to cut in the workpiece with the rake surfacebeing rotated and a pulling function to pull and flow out a chip by therotating rake surface are operated. Therefore, according to this cuttingmachining, the above functions and a peripheral speed of the cuttingtool being equal to or more than a cutting speed of the cutting tool, aswell as the dispersion of the cutting heat generated at the cutting edgeon the entire outer circumferential surface due to the rotation of thecutting tool, cause the reduction of the cutting resistance force,thereby reducing the temperature generated at the cutting edge.Accordingly, it is possible to perform cutting a difficult-to-cutmaterial at a high efficiency, and the tool life can be improved.Furthermore, since the end surface of the cutting tool functions as arelief surface, the cutting edge of the cutting tool is approximately inparallel with the cutting machining surface, and therefore, the cuttingedge is unlikely to come in contact with the cutting machining surfacenot depending on rotation deflection of the tool. Thus, the cuttingaccuracy of the cutting machining surface can be improved.

(Cutting Method)

The method for cutting according to the present invention includes astep for rotating an outer peripheral surface of the cutting tool aboutan axis line of the cutting tool and a step for performing cuttingmachining on the workpiece by making the cutting tool travel relative tothe workpiece, having an outer peripheral surface and an end surface ofthe cutting tool function as a rake surface and a relief surface,respectively, and by controlling a peripheral speed of the cutting toolto be equal to or more than a cutting speed of the cutting tool. Thesame or similar effects obtained by the cutting device of the presentinvention explained above can be obtained by the cutting method of thepresent invention.

BRIEF EXPLANATION OF ATTACHED DRAWINGS

FIG. 1 is a plan view of the entire structure of the cutting deviceassociated with an embodiment of the present invention;

FIG. 2A is a front elevational view of a cutting tool used in thecutting device according to FIG. 1;

FIG. 2B is a side elevational view of the cutting tool according to FIG.2A;

FIG. 3 is a flowchart explaining a cylindrical cutting control byfeeding in a plunge cutting direction using the cutting tool accordingto FIG. 2A and FIG. 2B;

FIG. 4A is a view showing a workpiece seen from a rotation axis linedirection thereof under the state of cylindrical cutting by feeding inthe plunge cutting direction by the cutting tool according to FIG. 2Aand FIG. 2B;

FIG. 4B is a view of the workpiece seen in a right angle directionrelative to the rotation axis line direction according to FIG. 4A;

FIG. 5 is a view for explaining an image of cross-cutting function bysetting a plunge cutting direction as a horizontal axis and across-cutting direction as a vertical axis;

FIG. 6 is a view showing a comparison in largeness by overlappingbetween an apparent blade edge angle of the cutting tool uponcross-cutting and a blade edge angle of the cutting tool uponplunge-cutting;

FIG. 7 is a view showing an actually measured relationship between atool peripheral speed and a cutting resistance;

FIG. 8A is a view of the workpiece seen from the rotation axis linedirection, indicating an imaging direction when taking an image of theworkpiece by a high speed camera under the cylinder cutting state,feeding in the plunge cutting direction by the cutting tool according toFIGS. 2A and 2B;

FIG. 8B is a view of the workpiece seen from a right angle directionrelative to the rotation axis line in FIG. 8A;

FIG. 9A is a first view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 9B is a second view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 9C is a third view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 9D is a fourth view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 9E is a fifth view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 9F is a sixth view indicating the image taken by the high speedcamera by changing the peripheral speed ratio;

FIG. 10A is a view showing a relationship between a chip flowing outangle and the peripheral speed ratio;

FIG. 10B is a view showing a relationship between a chip flowing outspeed ratio and the peripheral speed ratio;

FIG. 10C is a view showing a relationship between the chip flowing outangle and the chip flowing out speed ratio;

FIG. 11A is a perspective view indicating a state of cutting by a rotarytool;

FIG. 11B is a view seen from the rotation axis line of the workpieceshown in FIG. 11A;

FIG. 12A is a front elevational view of the cutting tool according to afirst modified embodiment used in the cutting device of FIG. 1;

FIG. 12B is a front elevational view of the cutting tool according to asecond modified embodiment used in the cutting device of FIG. 1;

FIG. 12C is a front elevational view of the cutting tool according to athird modified embodiment used in the cutting device of FIG. 1;

FIG. 13 is a front elevational view of the cutting tool according to afourth modified embodiment used in the cutting device of FIG. 1;

FIG. 14A is a view of the cutting tool seen from the front side thereofin a right angle direction relative to the rotation axis line of theworkpiece indicating a cylindrical cutting state feeding in a traversedirection by the cutting tool according to FIG. 2A and FIG. 2B;

FIG. 14B is a view of the cutting tool seen from the side thereof in aright angle direction relative to the rotation axis line of theworkpiece according to FIG. 14A;

FIG. 15A is a view of the workpiece seen from a right angle directionrelative to the plan of the workpiece indicating a plan surface cuttingstate by the cutting tool according to FIG. 2A and FIG. 2B; and

FIG. 15B is a view of FIG. 15A seen from a direction parallel to theplan surface.

EMBODIMENTS FOR IMPLEMENTING INVENTION

(Mechanical Structure of Cutting Device)

As shown in FIG. 1, the cutting device 1 is formed by a spindle head 10,a bed 20, a tailstock 30, a reciprocating table 40, a feed table 50, atilt table 60, a tool rest 70 and a control device 80. It is noted herethat in the description hereinafter, the axis line direction of a rotarymain spindle 11 provided on the spindle head 10 is referred to as a “Z”axis direction, a direction crossing at right angles with the axis linedirection of the rotary main spindle 11 within a horizontal plane isreferred to as “X” axis line direction.

The spindle head 10 is formed in a rectangular parallelepiped shape andis provided on the bed 20. The rotary main spindle 11 is rotatablyprovided on the spindle head 10. A chuck 12 is attached to one side ofthe rotary main spindle 11 and is provided with a pawl portion 12 awhich is capable of holding the peripheral surface of one end side of aworkpiece W. The rotary main spindle 11 is rotatably driven by a mainspindle motor 13 which is accommodated in the spindle head 10.

The bed 20 is formed in a rectangular parallelepiped shape and isprovided on a floor extending in the “Z” axis direction from the spindlehead 10 under the lower portion of the rotary main spindle 11. A pair of“Z” axis guide rails 21 a, 21 b is provided on the upper surface of thebed 20, extending in the “Z” axis direction and in mutually parallelwith each other so that the tailstock 30 and the reciprocating table 40are slidably guided thereby. Further, a “Z” axis ball screw (not shown)is provided on the bed 20 between the pair of “Z” axis guide rails 21 aand 21 b for driving the reciprocating table 40 in the “Z” axisdirection. A “Z” axis motor 22 is provided for rotatably driving the “Z”axis ball screw.

The tailstock 30 is provided on the pair of “Z” axis guide rails 21 aand 21 b to be movable in the “Z” axis direction relative to the bed 20.The tailstock 30 is provided with a center 31 which is capable ofsupporting a free end surface of the workpiece W held by the chuck 12.In other words, the center 31 is provided on the tailstock 30 so thatthe axis line of the center 31 agrees with the axis line of the rotarymain spindle 11.

The reciprocating table 40 is formed in a rectangular plate shape and isprovided between the spindle head 10 and the tailstock 30 on the pair of“Z” axis guide rails 21 a and 21 b so that the reciprocating table 40 ismovable in the “Z” axis direction relative to the bed 20. A pair of “X”axis guide rails 41 a and 41 b is provided on the upper surface of thereciprocating table 40, extending in the “X” axis direction and inmutually parallel with each other so that the feed table 50 is slidablyguided thereby. Further, an “X” axis ball screw (not shown) is providedon the reciprocating table 40 between the pair of “X” axis guide rails41 a and 41 b for driving the feed table 50 in the “X” axis direction.An “X” axis motor 42 is provided for rotatably driving the “X” axis ballscrew.

The feed table 50 is formed in a rectangular plate shape and is providedbetween the pair of “X” axis guide rails 41 a and 41 b so that the feedtable 50 is movable in the “X” axis direction relative to thereciprocating table 40. A pair of tilt table support portions 61 isprovided on an upper surface of the feed table 50 with a predetermineddistance apart from each other in the “Z” axis direction. The pair oftilt table support portions supports the tilt table 60.

The tilt table 60 is formed in a cradle shape and is supported by thepair of tilt table support portions 61 so that the tilt table 60 isrotatable (swingable) about the “Z” axis line. The tool rest 70 isarranged on the upper surface of the tilt table 60. One of the pair oftilt table support portions 61 is provided with a tilt motor 62 whichrotatably (swingably) drives the tilt table 60 about the “Z” axis line.

A tool holder 71 is provided at the tool rest 70 to be rotatable aboutthe “X” axis line. A tool motor 72 is provided at the tool rest 70 forrotatably driving the tool holder 71 about the “X” axis line. A cuttingtool 90, which will be explained later, is chucked by the tool holder 7.Further, the tool rest 70 is provided with a supply nozzle 73 which isconnected to a cutting oil supply device (not shown) by which a cuttingoil is supplied for cooling the cutting tool 90.

The control device 80 includes a spindle rotation control portion 81, areciprocating table movement control portion 82, a feed table movementcontrol portion 83, a tilting control portion 84 and a tool rotationcontrol portion 85. It is noted here that each control portion 81through 85 may be formed separately by individual hardware, respectivelyor may be structured so as to perform respective functions by usingsoftware.

The spindle rotation control portion 81 rotatably drives the rotary mainspindle 11 with a predetermined rotation speed by controlling the mainspindle motor 13. The reciprocating table movement control portion 82reciprocates the reciprocating table 40 along the pair of “Z” axis guiderails 21 a and 21 b by controlling the “Z” axis motor 22.

The feed table movement control portion 83 reciprocates the feed table50 along the pair of “X” axis guide rails 41 a and 41 b by controllingthe “X” axis motor 42. The tilting control portion 84 rotatably(swingably) drives the tilt table 60 about the “Z” axis line bycontrolling the tilt motor 62. The tool rotation control portion 85rotatably drives the cutting tool 90 together with the tool holder 71 bycontrolling the tool motor 72.

The control device 80 controls the tilt motor 62 to incline the cuttingtool 90 with a predetermined angle. Then, the control device 80 controlsthe main spindle motor 13 and the tool motor 72 to rotate the workpieceW as well as the cutting tool 90. The workpiece is rotated to make thecutting tool travel relative to the workpiece W. Further, the controldevice 80 controls the “X” axis motor 42 to relatively move theworkpiece W and the cutting tool 90 in the “X” axis direction therebyperforming the cutting machining on the workpiece W by letting the outerperipheral surface of the cutting tool 90 cross-cut the workpiece W.

It is noted that the tool rest 70, the tool holder 71, the tool motor 72and the tool rotation control portion 85, etc., correspond to the“rotating means”, the spindle head 10, rotary main spindle 11, the mainspindle motor 13, the tailstock 30, the tool rest 70, the tool holder 71and the spindle rotation control portion 81, etc., correspond to the“traveling means” and the tilt table 60, the tilt table support portions61, the tilt motor 62 and the tilting control portion 84, etc.,correspond to the “inclining means”.

(Shape of Cutting Tool)

As shown in FIGS. 2A and 2B, the cutting tool 90 is formed by atruncated cone shaped tool main body 91 and a columnar shaped tool shaft92 which extends from the small diameter end surface 91 a of the toolmain body 91 positioned at the root portion of the tool main body 91.The outer peripheral surface of the tool main body 91 is formed tofunction as a rake surface 91 b. The large diameter end surface of thetool main body 91 is formed to function as a flat relief surface 91 c.

The ridgeline formed by the rake surface 91 b and the relief surface 91c of the tool main body 91 is formed to be in a continuing circularshape cutting edge 91 r, i.e., a circular cutting edge 91 r withnon-discontinuing portion. The cutting edge angle α of the cutting tool90, i.e., the angle α formed by the inclination line of the rake surface91 b seen from a direction perpendicular to the rotation axis line Rtand the straight line of the relief surface 91 c seen from a directionperpendicular to the rotation axis line Rt is set to be equal to or morethan 45 degrees, preferably from 70 to 80 degrees in order to keep thestrength of the cutting edge 91 r.

(Cutting Method Using Cutting Tool and Cutting Method Using Rotary Tool)

Next, the difference between the cutting method using the cutting tool90 and the cutting method using an existing rotary tool which isrelatively close to the cutting method using the cutting tool 90 will beexplained with a case of cutting a cylindrically shaped workpiece W. Asshown in FIGS. 11A and 11B, the rotary tool 100 is formed by a truncatedcone shaped tool main body 101 and a columnar shaped tool shaft 102which extends from the small diameter end surface 101 a of the tool mainbody 101. The large diameter end surface of the tool main body 101 isformed to function as a rake surface 101 b and at the peripheral brimportion of the rake surface 101 b, a cutting edge 101 c is formed whichis in a continuing circular shape, i.e., a non-discontinuing completecircular shape.

According to the cutting method using the rotary tool 100, the rotarytool 100 is rotated in an arrow “rr” direction shown in the drawings.The workpiece W is rotated in an arrow “rw” direction. Then the rotationaxis line Rr of the rotary tool 100 is set to be positionedperpendicular to the rotation axis line Rw of the workpiece W and inparallel with a tangential line Lw which passes the cutting point Pr ofthe cutting machining surface Ws (outer peripheral surface) of theworkpiece W. Under this state, the cutting edge 101 c of the rotary tool100 cross-cuts the cutting point Pr of the cutting machining surface Wsof the workpiece W. Thus the cutting machining surface Ws of theworkpiece W is cut in the peripheral direction.

During the cutting machining of the workpiece W, the rotary tool 100slightly deflects by receiving a cutting resistance at the cutting pointPr, but the direction of deflection vr is perpendicular to the rotationaxis line Rw of the workpiece W and passing through the cutting pointPr, which is the direction intersecting perpendicularly with the cuttingtraveling direction G. Accordingly, the cutting edge 100 c of the rotarytool 100 is periodically moved away in a radial direction from thecutting machining surface Ws of the workpiece W by the deflection and aninfluence of a rotation deflection of the rotary cutting tool 100 duringcutting machining may be easily transferred on to the cutting machiningsurface Ws of the workpiece W. Thus, the cutting accuracy of the cuttingmachining surface Ws of the workpiece W may tend to be worsening.

On the other hand, as shown in FIG. 4A, first, the control device 80controls the cutting tool 90 so that the rotation axis line Rt of thecutting tool 90 is set to be inclined by a predetermined angle θ towarda cutting traveling direction Gp from the state that the rotation axisline Rt is in parallel with the normal of the cutting point Pt. Indetail, the straight line Lt, which is perpendicular to the rotationaxis line Rw of the workpiece W and is in contact with the cutting pointPt, is inclined by a predetermined angle θ from a cutting travelingdirection Gp centering around the rotation axis line Rw of the workpieceW to obtain a straight line Lc and then the rotation axis line Rt of thecutting tool 90 is inclined to be in parallel with the obtained straightline Lc. Thus, the contact between the relief surface 91 c of thecutting tool 90 and the cutting machining surface Ws of the workpiece Wcan be avoided.

As shown in FIGS. 4A and 4B, according to the cutting method using thecutting tool 90, although the cutting tool 90 may slightly deflect bythe cutting resistance force received at the cutting point Pt, thedirection of deflection vt is inclined by an angle θ in an inclineddirection of the cutting tool 90 relative to the direction of thestraight line Lt perpendicular to the rotation axis line Rw of theworkpiece W and passing through the cutting point Pt, that is, thedirection rotated by the supplementary angle of the inclined angle θ(180−θ) degree relative to the cutting traveling direction Gp.Accordingly, the periodical separation of the cutting edge 91 r of thecutting tool 90 from the cutting machining surface Ws of the workpiece Win a radial direction caused by the deflection becomes less frequent andan influence of the rotation deflection of the cutting tool 90 duringcutting machining becomes very difficult to be transferred on to thecutting machining surface Ws of the workpiece W. Thus, the cuttingaccuracy of the cutting machining surface Ws can be improved.

Next, as shown in FIGS. 4A and 4B, the control device 80 rotates therake surface 91 b of the cutting tool 90 about the rotation axis line Rtin a rotation direction rt and at the same time rotates the workpiece Wabout the rotation axis line Rw in a rotation direction rw, thereby toperform cutting machining on the cutting machining surface Ws of theworkpiece W. According to the rotary tool 100, the large diameter endsurface of the tool main body 101 serves as the rake surface 101 b whencutting machining is performed, but according to the cutting tool 90,the cutting machining is performed such that the rake surface 91 b ofthe cutting tool 90 is rotated to perform a cross-cutting function tocut-in the cutting machining surface Ws and to perform a pullingfunction to pull and flow out a chip K by the rotating rake surface 91 bof the cutting tool 90.

FIG. 5 is an explanatory view explaining an image of the cross-cuttingoperation, wherein the horizontal axis indicates the plunge cuttingdirection and the vertical axis indicates the cross-cutting direction.The cutting edge angle α of the cutting tool 90 can be considered to bethe cutting edge angle when the cutting machining is performed by plungecutting operation where the cutting tool 90 is not rotated. Therefore,by setting the cutting edge 91 r as the intersecting point of thehorizontal and vertical axes and the relief surface 91 c as thehorizontal axis, when the cutting tool 90 is seen from the directionperpendicular to the rotation axis line in FIG. 5, the cutting edgeangle α can be regarded as the angle formed by the rake surface 91 b andthe relief surface 91 c. Then, the nominal cutting edge angle β of thecutting tool 90 upon cross-cutting is considered to be the cutting edgeangle of the cutting tool 90 upon cutting machining when the cuttingtool 90 is rotated. Accordingly, the nominal cutting edge angle β is theangle formed by the lines m and m′ which are formed by connecting bothends of a line “t” with the cutting edge 91 r. The line “t” is formed bytranslating a randomly selected line that passes the rake surface 91 band the relief surface 91 c, in a cross-cutting direction.

As is apparent from FIG. 6, the nominal cutting edge angle β of thecutting tool 90 upon cross-cutting is more acute than the cutting edgeangle α of the cutting tool 90 upon plunge cutting operation. Thus,according to the cutting machining using the cutting tool 90, thecutting resistance force can be reduced to thereby lower the temperatureof the cutting edge 91 r. Therefore, the tool life of the cutting tool90 can be improved. Further, the sheer angle δ (See FIG. 4B) of thecutting tool 90, i.e., the angle formed by the flow out direction of thechip K and the cutting traveling direction Gp becomes larger than thesheer angle formed at the cutting machining under the plunge cuttingoperation, where the cutting machining is performed by plunge cuttingwithout rotating the cutting tool 90. Thus, the reduction of the cuttingresistance force by the cutting machining using the cutting tool 90 canbe achieved and the temperature of the cutting edge 91 r can be alsoreduced and accordingly, the tool life of the cutting tool 90 can beimproved.

FIG. 7 shows a relationship between the actually measured peripheralspeed V of the cutting tool 90 (hereinafter referred to as “toolperipheral speed”) and the cutting resistance N. The tool peripheralspeed V is a rotation speed at the cutting point Pt (See FIG. 4A) on thecutting edge 91 r. As the cutting resistance N, the inventors of theapplication measured a cutting resistance Nm (See FIG. 4A) in a maincomponent force direction perpendicular to the rotation axis line Rt ofthe cutting tool 90 and the rotation axis line Rw of the workpiece W atthe cutting point Pt, a cutting resistance Nb (See FIG. 4B) in a thrustcomponent force direction perpendicular to the rotation axis line Rt ofthe cutting tool 90 and in parallel with the rotation axis line Rw ofthe workpiece W (direction perpendicular to the main component forcedirection) and a cutting resistance Nr (See FIG. 3A) in a rotationaldirection of the cutting tool 90.

Further, as shown in FIG. 7, the cutting resistance Nm in the maincomponent force direction and the cutting resistance Nb in the thrustcomponent force direction are large when the tool peripheral speed V iszero (0), where the plunge cutting is performed. However, as the toolperipheral speed V increases, the values of the cutting resistance Nmand Mb become small and thereafter become approximately constant.Particularly, when the tool peripheral speed V becomes more than thevalue Va which is the same speed as the cutting speed, the values of thecutting resistance Nm and Mb are largely reduced. It is noted that thecutting resistance Nr in the rotational direction becomes graduallyincreased as the tool peripheral speed V becomes increased and thenfinally becomes approximately constant.

Further, when the tool peripheral speed V is zero (0), a short and thickchip K is flown out. However, as the tool peripheral speed V increases,a long and thin chip K, which length is equal to or more than a cuttingmachining distance, is flown out. (See FIGS. 4A and 4B). It is assumedthat the flowing out speed of the chip K is slower than the cuttingspeed when the tool peripheral speed V is zero and therefore the chip isplastically deformed and the chip K becomes thicker in thickness andshorter in length, however the flowing out speed of the chip K becomesfaster, as the tool peripheral speed V increases by the largely operatedcross-cutting and pulling functions, and therefore, the thickness of thechip becomes thinner and the length thereof becomes longer. As explainedabove, according to the cutting machining using the cutting tool 90, ahighly efficient cutting can be obtained in a cutting machining of adifficult-to-cut material, such as Titanium alloy or Inconel, the hightemperature thereof having been the problem upon cutting machiningthereof.

According to the cutting method using the cutting tool 90, the ratio ofperipheral speed between the tool peripheral speed and the peripheralspeed of the workpiece W (hereinafter, the latter is referred to as“workpiece peripheral speed” and the ratio of “tool peripheralspeed/workpiece peripheral speed” is referred to simply as “peripheralspeed ratio”, which corresponds to the “speed ratio” of the invention)plays a very important role on the result, etc., of the tool lifeimprovement. In other words, when the peripheral speed ratio changes,the friction work between the cutting tool 90 and the workpiece Wchanges, which leads to the frictional abrasion of the cutting tool 90.When the peripheral speed ratio is set to be 1.0, the friction workbetween the cutting tool 90 and the workpiece W becomes the minimumvalue and therefore the effect of the tool life improvement can beachieved.

As some examples of changing of the peripheral speed ratio, cuttingmachining of the workpiece W which outer peripheral surface is taperedor stepped, cutting machining of the workpiece W which needs machiningpath over a plurality of times and cutting machining of the end surfaceof the workpiece W can be raised. In these cases, since the diameter ofthe workpiece W (hereinafter referred to as “workpiece diameter”) ischanged during the cutting machining, the workpiece peripheral speedalso changes and further the peripheral speed ratio changes accordingly.As some other examples, the peripheral speed ratio changes due to thetool frictional abrasion or due to the tool re-grinding operation, etc.In these cases, the tool diameter of the cutting tool 90 changes andtherefore, the tool peripheral speed changes and eventually theperipheral speed ratio changes.

As shown in FIGS. 8A and 8B which correspond to the states of FIGS. 4Aand 4B, respectively, a high speed camera Ca is set to be able to takethe images seen from the arrow direction in the drawings. The controldevice 80 analyzes the images of the chip K flowing out state taken bythe high speed camera Ca, by changing the peripheral speed ratio from0.0 to 2.0. Thus, the chip K flowing out angle formed by the flowing outdirection of the chip K relative to the cutting edge 91 r of the cuttingtool 90.

As the result, as shown in FIGS. 9A and 10A, when the peripheral speedratio is 0.0 (rotation of the cutting tool 90 is stopped), the chip K isflown out from the cutting edge 91 r in a perpendicular direction to thestraight line Lt, i.e., the chip K is flown out with a flowing out angleof 90 degrees. Then, as shown in FIGS. 9B through 9F and FIG. 10A, thechip K flowing out angle becomes gradually reduced in the rotationaldirection “rt” of the cutting tool 90 from the flowing out angle of 90degrees at the peripheral speed ratio of 0.0, as the peripheral speedratio becomes increased from the ratio of 0.2 to 2.0. Thus, theinventors found out that the flowing out angle changed from 70 degreesto 31 degrees.

Then, the inventors analyzed the images taken by the high speed cameraCa and obtained the flowing out speed of the chip K. The result of theanalysis is illustrated in FIG. 10B, wherein it was confirmed that whenthe peripheral speed ratio becomes equal to or more than 0.2, the ratiobetween the chip flowing out speed and the workpiece peripheral speed(hereinafter referred to as “flowing out speed ratio”) becomes large. Itis considered that the pulling function of the chip K can be more easilyobtained when the flowing out angle is small and the flowing out speedratio is large. In view of this observation and the results thereofshown in FIGS. 10A and 10B, the peripheral speed ratio is set to be 0.2or more and the chip K flowing out angle is set to be from 30 degrees to70 degrees.

Further, by setting the peripheral speed ratio to 1.0, the friction workbetween the cutting tool 90 and the workpiece W becomes minimum and thetool life improvement effect can be obtained. Further, when theperipheral speed ratio becomes 2.0, the chip K repeats segmentationafter the length of the chip K becomes a predetermined value.Accordingly, by setting the peripheral speed ratio to be less than 2.0,the connected chips K can be flown out continuously. Further, when thecutting machining is continued by the peripheral speed ratio of aconstant value exceeding 2.0, the friction work between the chips K andthe workpiece W increases which may tend to reduce the tool life. Fromthese observation points and the result thereof shown in FIG. 10C, theperipheral speed ration is set to be equal to or more than 1.0 and lessthan 2.0 and the flowing out speed ratio is set to be equal to or morethan 0.5 and equal to or less than 1.3. It is noted here that in orderto achieve the tool life improvement effect by minimizing the frictionwork between the cutting tool 90 and the workpiece W and yet to preventchips K from getting entangled in the workpiece W or the like bycontinuously flowing out the connected chips K, the peripheral speedratio is preferably set to be equal to or more than 1.0 and equal to orless than 2.0.

(Cutting Control Using Cutting Tool)

Next, the control using the cutting tool 90 for cutting the cylindricalworkpiece W by rotating the workpiece W in the axis line Rw thereof,feeding in a plunge cutting direction will be explained. According tothe cutting using the cutting tool 90, the control is made to maintainthe peripheral speed ratio to be constant within a certain range. Suchcontrol will be explained with reference to the flowchart shown in FIG.3.

The control device 80 obtains the tool diameter (Step S1: FIG. 3) andthen obtains the workpiece diameter (Step S2: FIG. 3). It is noted herethat the tool diameter is obtained by actually measuring using themeasurement device. The tool diameter may be either a diameter of theactually measured relief surface 91 c (cutting edge 91 r), i.e., adiameter of the circle perpendicular to the rotation axis line Rt whichpasses through the cutting point Pt in FIG. 4A or a diameter at a middleportion of the contact length between the cutting wedge 91 r and thechip K at the actually measured rake surface 91 b, i.e., a diameter of acircle perpendicular to the rotation axis line Rt passing through thepoint Px in FIG. 4A. The diameter of the workpiece W can be obtainedbased on the design drawing and an NC program.

Next, the control device 80 calculates the tool peripheral speed basedon the obtained tool diameter (Step S3: FIG. 3, corresponding to theperipheral speed obtaining means of the invention) and calculates theworkpiece peripheral speed based on the obtained workpiece diameter(Step S4; FIG. 3, corresponding to the “traveling speed obtaining means”of the invention). The tool peripheral speed V is a rotation speed atthe cutting point Pt (in FIG. 4A) on the cutting edge 91 r and isrepresented by the following numerical formula (1) by the tool diameterD and the spindle rotation speed N of the rotary main spindle 11. Theworkpiece peripheral speed “v” is a rotation speed at the cutting pointPt (in FIG. 4A) on the cutting machining surface Ws and is representedby the numerical formula (2) by the workpiece diameter d and theworkpiece rotation speed “n” of the workpiece W.[M1]V=n·D·N  (1)[M2]v=n·d·n  (2)

Next, the control device 80 judges whether the calculated workpieceperipheral speed is a value equal to or less than a predetermined upperlimit value which would not largely influence on the abrasion of cuttingtool 90 or not (Step S5: FIG. 3) and if judged that the workpieceperipheral speed exceeds the predetermined upper limit value, thecontrol device 80 changes the rotation speed of the workpiece W (StepS6: FIG. 3) and returns the program step to the step S2 and repeats thepreceding processes. The change of the rotation speed of the workpiece Wis made with the range of ±6%˜±10% relative to the current rotationspeed of the workpiece W.

On the other hand, at the step S5, when the control device 80 judgesthat the workpiece peripheral speed is equal to or less than thepredetermined upper limit value, the control device 80 calculates theperipheral speed ratio based on the calculated tool peripheral speed andthe workpiece peripheral speed (Step S7 in FIG. 3, corresponding to the“speed ratio calculating means” of the invention). The peripheral speedratio “y” is represented by the following numerical formula (3) by thetool peripheral speed V and the workpiece peripheral speed “v”.[M3]y=V/v  (3)

Next, the control device 80 judges whether the calculated peripheralspeed ratio exceeds a predetermined range or not (Step S8: FIG. 3) andif it is judged that the peripheral speed ratio exceeds thepredetermined range, the control device 80 changes the rotation speed ofthe cutting tool 90 (Step S9; FIG. 3) and returns the program step tothe step S2 and repeats the preceding processes. On the other hand, whenthe control device 80 judges that the peripheral speed ratio is withinthe predetermined range, the control device 80 continues the cuttingmachining and returns the program step to the step S2 and repeats thepreceding processes. It is noted that the “predetermined range” meansfor example the range of ±10%˜±20% relative to the value “1.0”. Further,the change of the rotation speed of the cutting tool 90 is made with therange of ±5%˜±10% relative to the current rotation speed of the cuttingtool 90. The above processes continue until the cutting machining of thecylindrical workpiece W ends.

(Other Embodiments of Cutting Tool)

According to the above embodiment, the rake surface 91 b of the cuttingtool 90 is formed to have a constant friction coefficient over thesurface. However, as shown in FIGS. 12A, 12B and 12C, the rake surfaces91 ba, 91 bb, and 91 bc of the cutting tools 90A, 90B and 90C may beformed to have different friction coefficients over the respectivesurfaces. In other words, the cutting tool 90A shown in FIG. 12A has therake surface 91 ba formed by an area Ah having a high frictioncoefficient and an area AI having a low friction coefficient which aremutually arranged in a circumferential direction.

In the above case, when the lengths in circumferential direction of bothareas Ah and AI are set to be the same length, the friction coefficientof the rake surface 91 b becomes closer to the constant coefficient andthe cross-cutting effect may be lessened. Accordingly, the length in thecircumferential direction of the area Ah having high frictioncoefficient is set to be longer than the length in the circumferentialdirection of the area AI having low friction coefficient not to lessenthe cross-cutting effect. The cutting tool 90B shown in FIG. 12B has therake surface 91 bb formed by the area Ah having the high frictioncoefficient and the area AI having the low friction coefficient each ofwhich is arranged in the half of the rake surface 91 bb in thecircumferential direction. The cutting tool 90C shown in FIG. 12C hasthe rake surface 91 bc formed by the area AI having the low frictioncoefficient, but the area Ah which friction coefficient is higher thanthe area AI is provided in a portion of the area AI having the lowfriction coefficient.

According to the cutting tools 90A, 90B and 90C, since the area Ahhaving high friction coefficient is in contact with the chip K for along period of time, the chip flowing out can be accelerated. The areaAl having low friction coefficient is formed by coating adiamond-like-carbon, for example. It is noted here that the ratiobetween the area Ah having the high friction coefficient and the area Alhaving the low friction coefficient is not limited to the ratioexplained above and any randomly selected ratio may be applied.

According to the above embodiment, the cutting edge 91 r is formed to bea continuing circular shape cutting edge 91 r, i.e., a circular cuttingedge 91 r with non-discontinuing portion. However, as shown in FIG. 13,a portion of the cutting edge 91 rd of the cutting tool 90D is providedwith a groove 91 d having a predetermined width 91 dw, i.e., the cuttingedge 91 rd is formed in a dis-continuing circular shape. The groove 91 dis formed, extending along the rake surface 91 b from the relief surface91 c to the small diameter end surface 91 a having the predeterminedwidth 91 dw. The cutting chip is divided into parts when the chip passesthrough the groove 91 d. This enables an easy post treatment for thechips. It is noted that the number of groove is not limited to one, thegroove may be provided at two or more portions.

According to the embodiment, the tool main body 91 of the cutting tool90 is formed in a shape of a truncated cone. However, the tool main bodymay be formed in a columnar shape or a reverse truncated cone shape orthe like, as long as the sectional plane perpendicular to the axis as awhole is in an annular shape. Further, an odd-even shaped portion of apetal shaped circle may be included as a circular shape. It is notlimited to a strict circular shape, as long as the cutting tool isprovided with a rake surface and a cutting edge at the circumferentialsurface side and functions as the rotary tool which pulls the chip bythe rake surface. In case of forming such shape, the relief surface mayinterfere with the workpiece W when the rake surface is formed as apositive side and therefore, the relief surface should be formed as anegative side or a portion forming the relief surface should be recessedto prevent the interference with the workpiece W.

(Others)

According to the embodiment explained above, the cutting machining isperformed under the state that the rotation axis line Rt of the cuttingtool 90 is inclined by a predetermined angle θ in a cutting travelingdirection from the state that the rotation axis line Rt is in parallelwith the normal line of the cutting point Pt under the controlling ofthe cylindrical cutting by feeding in the plunge cutting direction usingthe cutting tool 90. However, the cutting machining may be performedunder the state that the rotation axis line Rt of the cutting tool 90 isin parallel with the normal line of the cutting point Pt.

Further, under the constant peripheral speed ratio control, as the toolperipheral speed, the peripheral speed at the cutting edge 91 r formedby the rake surface 91 b and the relief surface 91 c of the cutting tool90 is used, however, as the tool peripheral speed, a peripheral speed atthe intermediate portion in the axis line Rt of the cutting tool 90 atthe rake surface 91 b or a mean peripheral speed of the entire area ofthe rake surface 91 b may be used. Still further, as the tool peripheralspeed, the peripheral speed at a portion other than the intermediateportion in the axis line Rt at the rake surface 91 b or a meanperipheral speed of a partial area (such as the area where the chip K isin contact) of the rake surface 91 b may be used. The area of the rakesurface 91 b which is the area of calculating the mean peripheral speedmay be the outer peripheral surface portions including the cutting edge91 r, or the cutting edge 91 r is considered as a different area of therake surface 91 b and as such the cutting edge 91 r may be excluded fromthe area of measuring the mean peripheral speed. Further, when theconstant peripheral speed ratio control is performed, the peripheralspeed ratio should be within the predetermined range value. However, itmay be always controlled to keep the peripheral speed ratio to the valueof “1.0”.

Further, in the constant peripheral speed ratio control, the peripheralspeed ratio is calculated based on the tool peripheral speed and theworkpiece peripheral speed. However, the peripheral speed ratio can beobtained by setting the relationship between the chip K flowing outspeed and the peripheral speed ratio in advance and then by obtainingthe chip K flowing out speed upon actual cutting machining. The chip Kflowing out speed can be obtained by analyzing the images taken by thehigh speed camera, or by setting the relationship between the thicknessof the chip and the chip K flowing out speed in advance, and bymeasuring the thickness of the chip upon actual cutting machining.

Various types of control can be applied for a control using a flowingout angle/speed ratio control means, as long as the above explainednumerical ranges are used as the machining conditions. The operatingconditions of the cutting device, by which the above numerical rangescan be obtained, are obtained in advance by measuring by theexperimental work or obtained by analyzing the measured result measuredreal-time during machining to reflect the results on the control device80. Further, the following controlling may be included, wherein in spiteof the feed-back from the measurement in advance and the real-timemeasurement, as a result of appropriate control of the cutting device 1by the control device 80, the machining conditions which include theabove numerical ranges can be obtained as the result system. This casecan be applicable to the control by the flowing out speed/speed ratiocontrol means and the control by the flowing out speed ratio controlmeans.

According to the above embodiment, the explanation of the machining ofthe case, that the cutting machining surface Ws of the cylindricalworkpiece W is cut in a circumferential direction, i.e., the case thatthe machining is performed by feeding the workpiece in X direction(plunge cutting feeding direction). However, the case that the machiningis performed by making the workpiece travel in Z (traverse) direction issimilarly performed. In other words, as shown in FIGS. 14A and 14B, therotation axis line Rt of the cutting tool 90 is set to be inclined fromthe state that the axis line Rt is in parallel with the normal line ofthe cutting point Pt to the state that the axis line Rt is inclined by apredetermined angle θ with the normal line toward the cutting travelingdirection Gt. Then, by rotating the rake surface 91 b of the cuttingtool 90 about the rotation axis line Rt in a rotation direction “rt” andat the same time rotating the workpiece W about the rotation axis lineRw in a rotation direction “rw”, and by making the cutting tool 90travel in a direction parallel with the rotation axis line Rw or makingthe workpiece W travel in a direction parallel with the rotation axisline Rw without making the cutting tool 90 travel, the cutting machiningis performed on the cutting machining surface Ws of the workpiece W.

According to the embodiment, the grinding machining of a cylinder isexplained, but the cutting tool 90 can be applicable to the grindingmachining of a flat surface. In other words, as shown in FIGS. 15A and15B, the rotation axis line Rt of the cutting tool 90 is set to beinclined from the state that the axis line Rt is perpendicular to theflat cutting machining surface WWs of the workpiece WW to the state thatthe axis line Rt is inclined by a predetermined angle θ toward thecutting traveling direction Gt. Then, by rotating the rake surface 91 bof the cutting tool 90 about the rotation axis line Rt in a rotationdirection “rt” with a tool peripheral speed V and at the same time bymaking the cutting tool 90 travel along the cutting machining surfaceWWs of the workpiece WW with a traveling speed “v”, or making theworkpiece WW travel in a direction parallel with the cutting machiningsurface WWs of the workpiece WW without making the cutting tool 90travel. Thus, the cutting machining is performed on the surface WWs tobe cutting machined of the workpiece WW.

(Effects)

The cutting device 1 according to the embodiment includes a rotatingmeans 70, etc., for rotating a cutting tool 90, 90A, 90B, 90C and 90Dabout a rotation axis line Rt of the cutting tool 90, 90A, 90B, 90C and90D and a traveling means 40, etc., for making the cutting tool 90, 90A,90B, 90C and 90D travel relative to a workpiece W and WW, wherein therotating means 70, etc., and the traveling means 40, etc. perform acutting machining on the workpiece W and WW by making the cutting tool90, 90A, 90B, 90C and 90D travel relative to the workpiece, having anouter peripheral surface of the cutting tool 90, 90A, 90B, 90C and 90Drotate and function as a rake face 91 b, 91 ba, 91 bb and 91 bc.According to the cutting machining, the cutting tool 90, 90A, 90B, 90Cand 90D performs a cross-cutting function to cut in the workpiece W andWW, the rake surface 91 b, 91 ba, 91 bb and 91 bc being rotated and apulling function to pull and flow out a chip K with the rotating rakesurface 91 b, 91 ba, 91 bb and 91 bc thereof. Therefore, according tothe cutting machining, in addition to the dispersion of the cutting heatgenerated at the cutting edge 91 r and 91 rd due to the rotation of thecutting tool 90, 90A, 90B, 90C and 90D on the entire outercircumferential surface of the rake surface 91 b, 91 ba, 91 bb and 91bc, the reduction of the cutting resistance force by the above functionscan be achieved to reduce the temperature generated at the cutting edge91 r and 91 rd so as to improve the tool life.

Further, the rotating means 70, etc. and traveling means 40 etc. performcutting machining on the workpiece W and WW so that the peripheral speedof the cutting tool 90, 90A, 90B, 90C and 90D becomes equal to or morethan a cutting speed of the cutting tool 90, 90A, 90B, 90C and 90D. Inother words, the case that the peripheral speed ratio is 1.0 or more isincluded. When the peripheral speed ratio is equal to or more than 1.0,the flowing out speed that the chip K is pulled by the rake surface 91b, 91 ba, 91 bb and 91 bc and is flown out from the cutting point Ptbecomes equal to or more than a chip K generation speed by thecross-cutting function and therefore, the generated chip K keeps thetensioned state not to be loosened and a good machining result can beeasily obtained. It is noted here that in order not to generate a largefriction abrasion caused by the speed difference between the chip Kgeneration speed and the peripheral speed of the rake surface 91 b, 91ba, 91 bb and 91 bc, the peripheral speed ratio may be set equal to ormore than 1.0 and equal to or less than 10.0. Preferably, when theperipheral speed ratio is equal to or more than 1.0 and less than 2.0,the chip K can be easily continuously flown out.

It is noted however, that the peripheral speed ratio is not limited tothe ratio equal to or more than 1.0 and less than 1.0 may be included.Even when the peripheral speed ratio is less than 1.0, a good machiningresult, better than a conventional machining method, may be obtained bythe pulling force at the rake surface 91 b, 91 ba, 91 bb and 91 bc. Forexample, the peripheral speed ratio may be equal to or more than 0.2 andless than 1.0 not to increase the friction abrasion at the rake surface91 b, 91 ba, 91 bb and 91 bc due to a sliding of the chip K caused bythe cross-cutting function by the cutting tool 90, 90A, 90B, 90C and90D. Further, when the peripheral speed ratio is equal to or more than0.5 and less than 1.0, the chips K can be easily continuously flown out.Since the cutting resistance can be largely reduced due to thecross-cutting and the pulling functions. Thus, the heat generation ofthe cutting tool 90, 90A, 90B, 90C and 90D can be suppressed to improvethe tool life.

Further, since the chips K generated while the cutting machining isperformed are under tensioned state by the pulling function at the rakesurface 91 b, 91 ba, 91 bb and 91 bc, the interfering of the chips Kwith the cutting machining can be prevented and thus, a good machiningresult can be expected. Still further, since the peripheral speed of thecutting tool is defined to be a peripheral speed at a portion of therake surface 91 b, 91 ba, 91 bb and 91 bc or a mean peripheral speed atan area of the rake surface 91 b, 91 ba, 91 bb and 91 bc, with which thechips K generated at the cutting machining are in contact, a highlyaccurate peripheral speed can be obtained.

Further, the cutting device 1 includes an inclining means 60, etc., forinclining a rotation axis line Rt of a cutting tool 90, 90A, 908, 90Cand 90D. The inclining means 60, etc., inclines the rotation axis lineRt of the cutting tool 90, 90A, 90B, 90C and 90D in a cutting travelingdirection Gp, Gt and GG of the cutting tool 90, 90A, 90B, 90C and 90Dwith a predetermined angle to perform a cutting machining on a workpieceW and WW.

Therefore, the cutting tool 90, 90A, 90B, 90C and 90D deflects in adirection rotated by the supplementary angle of the inclination angle θrelative to the cutting traveling direction Gp, Gt and GG. On the otherhand, a rotary tool 100 in general deflects in a rotated direction withright angles relative to the cutting traveling direction Gp. Therefore,compared to the cutting edge 101 c of the rotary tool 100, the cuttingedge 91 r, and 91 rd of the cutting tool 90, 90A, 90B, 90C and 90Dperiodical separation from the cutting machining surface Ws and WW ofthe workpiece W and WW caused by the deflection. Thus, an influence of arotation deflection of the cutting tool 90, 90A, 90B, 90C and 90D maydifficult to be transferred on to the cutting machining surface Ws andWW. Thus, the cutting accuracy of the cutting machining surface Ws andWW can be improved.

Further, the cutting tool 90, 90A, 90B, 90C and 90D performs the cuttingmachining on the cylindrical workpiece W. This can obtain the workpieceW having a highly accurate cutting machining surface Ws. Also, thecutting tool 90, 90A, 90B, 90C and 90D performs the cutting machining onthe flat surface workpiece WW. This can obtain the workpiece WW having ahighly accurate cutting machining surface WWs.

Further, the cutting device 1 performs the cutting machining on theworkpiece W and WW by arranging the cutting tool 90, 90A, 90B, 90C and90D such that the rake angle becomes a positive angle value. Thus, thechips K can be smoothly flown out and the cutting resistance generatedat the cutting machining by the cutting tool 90, 90A, 90B, 90C and 90Dcan be largely reduced to thereby reduce the generation of the heat atthe cutting tool 90, 90A, 90B, 90C and 90D. Thus, the tool life can beimproved.

Further, the rake surface 91 b, 91 ba, 91 bb and 91 bc of the cuttingtool 90, 90A, 90B, 90C and 90D includes a circular shape at thesectional plane perpendicular to the axis. Thus, the structure of thecutting tool 90, 90A, 90B, 90C and 90D becomes simplified and becomeseasy to be manufactured. Accordingly, the cutting tool which is low inmanufacturing cost can be proposed. Further, the rake surface 91 b, 91ba, 91 bb and 91 bc of the cutting tool 90, 90A, 90B, 90C and 90Dincludes a truncated cone shape. According to the cutting tool 90, 90A,90B, 90C and 90D, the adjustment of the rake angle can be easilyperformed.

Further, the rake surface 91 b, 91 ba, 91 bb and 91 bc of the cuttingtool 90, 90A, 90B, 90C and 90D includes areas Ah and Al in acircumferential direction having different friction coefficients.According to the cutting tool 90, 90B and 90C, the discharging of thechips K can be accelerated at the area having a high frictioncoefficient. The rake surface 91 bd of the cutting tool 90D is providedwith a groove 91 d which can divide a chip K generated upon cuttingmachining into parts. According to the cutting tool 91D, since the chipsK are divided into parts when passing through the groove 91 d, this canfacilitate the post treatment of the chips. K

Further, a speed ratio constant control means is provided which controlsthe peripheral speed ratio v (speed ratio) between the peripheral speedV of the rake surface 91 b, 91 ba, 91 bb and 91 bc of the cutting tool90, 90A, 90B, 90C and 90D and the peripheral speed v of the workpiece W(traveling speed when the workpiece W is made to travel relative to thecutting tool 90, 90A, 90B, 90C and 90D) or the speed ratio v between theperipheral speed V of the rake surface 91 b, 91 ba, 91 bb and 91 bc ofthe cutting tool 90, 90A, 90B, 90C and 90D and the moving speed v of theworkpiece WW (traveling speed when the cutting tool 90, 90A, 90B, 90Cand 90D is made to travel relative to the workpiece WW) to be constantwithin a predetermined range. Thus, the speed ratio is always keptconstant when the cutting machining is performed and thus the tool lifecan be improved to realize a further highly efficient cutting machining.

Further, the speed ratio constant control means corresponds to thecontrol device 80 which controls at least one of the peripheral speed Vand the traveling speed v. The control device 80 includes a peripheralspeed obtaining means for obtaining the peripheral speed V, travelingspeed obtaining means for obtaining the traveling speed v and a speedratio calculating means for calculating the speed ratio v based on eachspeed V and v which is obtained by the peripheral speed obtaining meansand the traveling speed obtaining means, wherein the control device 80controls at least one of the peripheral speed V and the traveling speedv so that the speed ratio v is kept within a predetermined range, whenthe speed ratio v calculated by the speed ratio calculating meansexceeds the predetermined range. Thus, even when the shape of theworkpiece W is changed, the peripheral speed ratio can be highlyaccurately kept to be constant to thereby elongate the tool life andfurther high efficiency can be achieved.

The workpiece W is a cylindrical object which rotates about the axisline Rw and the traveling speed v thereof corresponds to the peripheralspeed of the cutting machining surface Ws (outer peripheral surface) ofthe workpiece W in a rotation direction. Therefore, the cuttingmachining of the cutting machining surface Ws of the workpiece W can behighly efficiently performed. Further, the workpiece WW is an objectwhich is movable in a direction parallel with the cutting machiningsurface WWs (flat surface) and the traveling speed v thereof correspondsto the moving speed in a moving direction of the workpiece WW.Therefore, the cutting machining of the cutting machining surface WWs ofthe workpiece WW can be highly efficiently performed.

Further, the rake surface 91 b, 91 ba, 91 bb, 91 bc and 91 d of thecutting tool 90, 90A, 90B, 90C and 90D is in the shape of truncated coneand the peripheral speed v thereof corresponds to the peripheral speedat the cutting edge 91 r and 91 rd formed by the rake surface 91 b, 91ba, 91 bb, 91 bc and 91 d of the cutting tool 90, 90A, 90B, 90C and 90Dand the relief surface 91 c. Thus, the frictional abrasion at thecutting edge 91 r and 91 rd can be reduced.

Further, the rake surface 91 b, 91 ba, 91 bb, 91 bc and 91 d of thecutting tool 90, 90A, 90B, 90C and 90D is in the shape of truncated coneand the peripheral speed v thereof corresponds to the peripheral speedat the intermediate portion of the rake surface 91 b, 91 ba, 91 bb, 91bc and 91 d in the axis line Rt direction of the cutting tool 90, 90A,90B, 90C and 90D. Thus, the rake surface 91 b, 91 ba, 91 bb, 91 bc and91 d can be uniformly frictionally abraded.

Further, the rake surface 91 b, 91 ba, 91 bb, 91 bc and 91 d of thecutting tool 90, 90A, 90B, 90C and 90D is in the shape of truncated coneand the peripheral speed v thereof corresponds to the mean peripheralspeed at the entire area of the rake surface 91 b, 91 ba, 91 bb, 91 bcand 91 d. Thus, the entire area of the rake surface 91 b, 91 ba, 91 bb,91 bc and 91 d including the cutting edge 91 r and 91 rd can beuniformly frictionally abraded. Further, the speed ratio constant meanscontrols the speed ratio v always to be 1.0. Thus, the friction workbetween the cutting tool 90, 90A, 90B, 90C and 90D and the workpieceWand WW becomes minimum and the tool life elongation effect can beobtained.

Further, the speed ratio constant control means controls the speed ratiov to be equal to or more than 0.2. Further, the speed ratio constantcontrol means controls the speed ratio v to be equal to or more than1.0. Further the speed ratio constant control means controls the speedratio v to be equal to or more than 2.0. Still further, a flowing outangle/speed ratio control means is provided for controlling the flowingout angle of the chip K upon performing cutting machining on theworkpiece W and WW by the cutting tool 90, 90A, 90B, 90C and 90D to beequal to or more than 30 degrees and equal to or less than 70 degreesand for controlling the speed ratio v between the peripheral speed atthe outer peripheral surface of the cutting tool 90, 90A, 90B, 90C and90D and the traveling speed when the cutting tool 90, 90A, 90B, 90C and90D is made to travel relative to the workpiece W and WW to be equal toor more than 0.2. By using the above defined numerical ranges, thepulling function of the chip K can be easily obtained, thereby to obtaina good machining result.

Further, the flowing out angle/speed ratio control means controls thespeed ratio v to be equal to or more than 1.0. Further, the speed ratioconstant control means controls the speed ratio v to be equal to or morethan 2.0. Further, the flowing out angle/speed ratio control meanscontrols the flowing out speed ratio between the chip K flowing outspeed upon performing cutting machining on the workpiece W and WW by thecutting tool 90, 90A, 90B, 90C and 90D and the peripheral speed of theouter peripheral surface of the cutting tool 90, 90A, 90B, 90C and 90Dto be equal to or more than 0.5 and equal to or less than 1.3 andcontrols the speed ratio v to be equal to or more than 0.2. The flowingout angle/speed ratio control means corresponds to the control device 80which controls at least one of the peripheral speed and the travelingspeed. By using the numerical ranges, the pulling function of the chip Kcan be easily obtained, thereby to obtain a good machining result.

Further, a flowing out speed/speed ratio control means is provided forcontrolling the flowing out speed ratio between the chip K flowing outspeed upon performing cutting machining on the workpiece W and WW by thecutting tool 90, 90A, 90B, 90C and 90D and the peripheral speed of theouter peripheral surface of the cutting tool 90, 90A, 90B, 90C and 90Dto be equal to or more than 0.5 and equal to or less than 1.3 andfurther controlling the speed ratio v between the peripheral speed ofthe outer peripheral surface of the cutting tool 90, 90A, 90B, 90C and90D and the traveling speed when the cutting tool 90, 90A, 90B, 90C and90D and the workpiece W and WW are relatively fed, to be equal to ormore than 0.2. The flowing out speed/speed ratio control meanscorresponds to the control device 80 which controls at least one of theperipheral speed and the traveling speed. By using the numerical ranges,the pulling function of the chip K can be easily obtained, thereby toobtain a good machining result.

Still further, a flowing out speed ratio control means is provided forcontrolling the flowing out angle of the chip K upon performing cuttingmachining on the workpiece W and WW by the cutting tool 90, 90A, 90B,90C and 90D to be equal to or more than 30 degrees and equal to or lessthan 70 degrees and controlling a flowing out speed ratio between thechip K flowing out speed upon performing cutting machining on theworkpiece W and WW by the cutting tool 90, 90A, 90B, 90C and 90D and theperipheral speed of the outer peripheral surface of the cutting tool 90,90A, 90B, 90C and 90D to be equal to or more than 0.5 and equal to orless than 1.3. The flowing out speed ratio control means corresponds tothe control device 80. By using the numerical ranges, the pullingfunction of the chip K can be easily obtained, thereby to obtain a goodmachining result.

The method for cutting according to the embodiment of the presentinvention includes steps of rotating an outer peripheral surface of thecutting tool 90, 90A, 90B, 90C and 90D about the rotation axis line Rtof the cutting tool 90, 90A, 90B, 90C and 90D and performing a cuttingmachining on a workpiece W and WW by making the cutting tool 90, 90A,90B, 90C and 90D travel relative to the workpiece W and WW, having theouter peripheral surface of the cutting tool function as a rake surface91 b, 91 ba, 91 bb and 91 bc and 91 d and by controlling a peripheralspeed of the cutting tool to be equal to or more than a cutting speed ofthe cutting tool. The end surface of the cutting tool 90, 90A, 90B, 90Cand 90D is formed to be a relief surface 91 c. Thus, the effectsobtained by the cutting device 1 can be obtained by this cutting method.

REFERENCE SIGNS LIST

1; cutting device, 70, 71, 72 and 85; rotating means, 40,21 a, 21 b, 22,50, 41 a, 41 b, 42, 82 and 83; traveling means, 60, 61, 62 and 84;inclining means, 90,90A, 90B, 90C and 90D; cutting tool, 91 b, 91 ba, 91bb and 91 bc; outer peripheral surface (rake surface) of tool main body,91 c; large diameter end surface (relief surface) of the tool main body,91 r, 91 rd; ridge line between the outer peripheral surface and thelarge diameter end surface of the tool main body (cutting edge), α;cutting edge angle, β; nominal cutting edge angle, θ; inclination angleof the rotation axis line of the cutting tool, Gp; GG; cutting travelingdirection, W; workpiece.

The invention claimed is:
 1. A cutting device comprising: a work holderconfigured to support a workpiece for rotation about a workpiecerotation axis; a tool holder configured to support a cutting tool forrotation about a tool rotation axis, wherein the tool rotation axis isoriented to the workpiece rotation axis such that when a workpiece ismounted to the work holder and rotated about the workpiece rotationaxis, and a cutting tool having an outer peripheral surface, and alsohaving an end surface extending perpendicular to the tool rotation axisand joining the outer peripheral surface at a cutting edge, is mountedto the tool holder and rotated about the tool rotation axis and causedto engage and cut the workpiece, the outer peripheral surface and theend surface function as a rake surface and a relief surface,respectively; and a controller having: means for controlling arotational speed about the tool rotation axis of the cutting toolmounted to the tool holder, means for controlling a rotational speedabout the workpiece rotation axis of the workpiece mounted to the workholder, means for providing relative movement of the tool holderrelative to the workpiece axis such that the cutting tool mounted to thetool holder and rotated about the tool rotation axis is caused to engagethe workpiece mounted to the work holder and rotated about the workpiecerotation axis, and to perform a cutting operation, and means for causinga cutting tool peripheral speed at the cutting edge during the cuttingoperation to be equal to or more than a cutting speed of the cuttingtool performing a cutting operation when the cutting tool mounted to thetool holder and rotated about the tool rotation axis engages theworkpiece mounted to the work holder and rotated about the workpiecerotation axis, and the cutting tool mounted to the tool holder issubject to the relative movement of the tool holder relative to theworkpiece axis, whereby said cutting speed is the result of therotational speed about the tool rotation axis of the cutting toolmounted to the tool holder, the rotational speed about the workpiecerotation axis of the workpiece mounted to the work holder, and therelative movement of the tool holder relative to the workpiece axis. 2.A cutting method comprising steps of: providing a workpiece to rotateabout a workpiece rotation axis; providing a cutting tool to rotateabout a tool rotation axis, the cutting tool having an outer peripheralsurface, and also having an end surface extending perpendicular to thetool rotation axis and joining the outer peripheral surface at a cuttingedge; causing the rotating cutting tool to engage the rotating workpieceand perform a cutting operation in which the outer peripheral surfaceand the end surface function as a rake surface and a relief surface,respectively during the cutting operation; and controlling a peripheralspeed of the cutting tool at the cutting edge during the cuttingoperation to be equal to or more than a cutting speed of the cuttingtool performing a cutting operation when the cutting tool mounted to thetool holder and rotated about the tool rotation axis engages theworkpiece mounted to the work holder and rotated about the workpiecerotation axis, and the cutting tool mounted to the tool holder issubject to the relative movement of the tool holder relative to theworkpiece axis, whereby said cutting speed is the result of therotational speed about the tool rotation axis of the cutting toolmounted to the tool holder, the rotational speed about the workpiecerotation axis of the workpiece mounted to the work holder, and therelative movement of the tool holder relative to the workpiece axis.